The present invention relates generally to optical equipment supporting devices and more particularly concerns a camera panhead.
In motion and television filming, it is often necessary to sweep a camera about a horizontal or vertical axis, or both, in order to cover a wide scene or follow a moving object. One of the most difficult functions that must be performed by a panhead is permitting the mounted camera or other instrument to be smoothly scanned back and forth, and up and down. Both fast and slow movement must be smooth and uniform, free from jerking or scattering when starting or stopping. Such movement may be difficult due to the inertia of the supported instrument and the frictional drag inherent in the mechanical operation of the panhead itself. Achieving smooth and uniform movement may be further complicated by other factors such as the substitution of supported instruments having different weights or centers of gravity, and environmental effects due to the broad temperature ranges in which the panhead is required to function. Consequently, to provide for maximum versatility and efficiency during usage, the panhead should provide precise movement and be light, and easily and quickly adjustable.
Various designs of fluid drag systems, such as those in U.S. Pat. Nos. 2,905,421, 2,998,953, and 3,180,603, have been utilized in panheads in order to provide smooth panning and tilting movements. While these systems operate effectively to provide adjustable uniform drag, many utilize systems in which an adjustment knob may have to be turned several revolutions in order to adjust the level of drag exerted by the fluid system. Such drag adjustment designs may be inappropriate for usage when an operator must quickly adjust the pan or tilt drag.
Further, a camera is often moved rapidly during use. The torque load resulting from such rapid panning or tilting movement may cause the drag components to automatically move or readjust, which results in imprecise movement due to backlash or slop.
A counterbalancing system is often used to counterbalance the weight of the mounted instrument to provide a smooth tilting movement. While the torque exerted by the tilting camera increases substantially linearly as the panhead tilts through small angles, the torque levels off and follows a generally sinusoidal curve as the tilt angle increases. Consequently, simple counterbalancing systems, such as linear springs, generally only operate effectively through low tilt angles. While more complicated counterbalancing systems, such as those using cam and roller devices, may operate more effectively through a wider range of tilt angles, many of these devices also do not work well at higher tilt angles.
Accordingly, it is a general aim of the invention to provide a panhead that smoothly and uniformly pans and tilts. Another object is to provide a panhead which provides precise movement with minimal backlash or slop.
A further object is to provide a panhead which effectively counterbalances the weight of a supported instrument by exerting a restoring torque approximately equal to the torque exerted by the tilting instrument. A related object is to provide a device which counterbalances the weight of the supported instrument without the use of cams and rollers. Another object is to provide a panhead which have a panning range of 360.degree. and a full tilt range 90.degree. from horizontal in both the upward and downward directions.
An additional object of the invention is to provide a counterbalancing system which may be easily adjusted for varying weights and heights of mounted equipment. A further object is to provide a fluid drag system which may be quickly and easily adjusted to desired degrees of drag for panning and tilting movements. A related object is to provide a panhead which may be locked at any desired angle, horizontally or vertically, without shifting the position of the supported instrument.